According to a recent study, customers value proper grammar more than anything else in their social media interactions with brands.

That's bad news for Pepsi, which makes more grammar errors on LinkedIn than Coke, and for General Motors, which gets things wrong more than Ford.

London agency Disruptive Communications took a poll of 1,003 British consumers this past July and asked them what factor would most likely damage their opinion of a brand on social media.

"Poor spelling or grammar" came in at 42.5 percent, far ahead of second-place "Updates are too 'sales-y'" at 24.9 percent.

It is interesting to note that among the 18-24 year-olds polled, the top choice was "Does not post updates enough" at 22.1 percent. A lack of activity got an almost equal amount of votes as bad grammar, which came in at 20.9 percent in that demographic.

Bottom line: customers pay more attention to the little things than brands may think.

The proofreading software service Grammarly decided to take a look at three of the world's biggest brand battles and see how the grammar on the competitors' LinkedIn pages stacked up: